Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus including an electrophotographic photosensitive member.
Description of the Related Art
Process cartridges and electrophotographic apparatuses are provided with electrophotographic photosensitive members, and currently mostly employ electrophotographic photosensitive members containing organic photoconductive substances. The electrophotographic photosensitive member typically includes a support and a photosensitive layer formed on the support. Between the support and the photosensitive layer, an undercoat layer is provided to suppress injection of charges from the support to the photosensitive layer (charge generating layer) to prevent generation of image defects such as fogging and cover defects on the surface of the support.
Some known undercoat layers contain electron transporting substances to suppress drawing of electrons from a charge generating layer and suppress injection of charges from the support to the charge generating layer. Such undercoat layers containing electron transporting substances have higher resistance and suppress the injection of charges from the support to the charge generating layer more significantly than undercoat layers utilizing conductive ions or metal oxide particles do.
Japanese Patent Application Laid-Open No. 2010-145506 describes an undercoat layer (electron transporting layer) including only a binder resin and a tetracarboxylic acid imide compound as an electron transporting material. The undercoat layer has high mobility and suppresses the injection of charges significantly. Since the electron transporting substance is soluble in a solvent, the electron transporting material may be eluted into the charge generating layer or a coating solution when the charge generating layer is formed on the undercoat layer by coating, particularly by immersion coating. For this reason, the undercoat layer cannot attain its intrinsic electron transportability, leading to insufficient electron moving ability in some cases.
This leads to techniques of crosslinking the electron transporting substance. Japanese Patent Application Laid-Open No. 2003-330209 describes an undercoat layer containing a polymerized product of an electron transporting substance having a non-hydrolyzable polymerizable functional group.
Such an undercoat layer can suppress the elution of the electron transporting substance by crosslinking thereof. Unfortunately, the crosslinking may cause insufficient drawing of electrons to stagnate charges, leading to insufficient sensitivity.
There has been plenty of room for improvement in formation of an undercoat layer having high electron moving ability without eluting an electron transporting substance when the charge generating layer is formed on the undercoat layer by coating.